What is the Mac terminal command to remove ACL?
Using chmod -a allows one to remove access control entries individually (as @geekosaur suggested).
But if you are looking to remove all ACLs from a file or folder, the solution is to use the brute-force option: chmod -N which removes all access control entries for a file or folder.
chmod -RN will do the same recursively for a folder and its entire contents.
It's all bundled into the chmod command; take a look at the -a/+a/=a options in the manpage.